From template to anchors: transfer of virtual pendulum posture control balance template to adaptive neuromuscular gait model increases walking stability (original) (raw)
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FMCH: A new model for human-like postural control in walking
2015 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2015
Spring loaded inverted pendulum (SLIP) model used simple spring mass mechanism to explain leg function and ground reaction force in legged locomotion. Balancing the upper body can be addressed by addition of a rigid trunk to this template model. The resulting model is not conservative and needs hip torque to keep the trunk upright during locomotion, like humans. Leg force modulated compliant hip (FMCH) is our new model for postural control in walking which employs the leg force feedback to adjust the hip compliance. Such an application of positive force feedback presents a new template for neuromuscular model. This method provides stable and robust walking in simulations and also mimics human-like kinetic behavior. Analyzing human walking experiment shows that FMCH can explain the hip torque-angle relation for different walking speeds. Finally, this approach may physically implement the virtual pendulum (VP) concept, observed in human/animal locomotion.
Stable running by leg force-modulated hip stiffness
Balancing the upper body as one of the main features in human locomotion is achieved by actuation of the compliant hip joints. Using leg force feedback to adjust the hip spring is presented as a new postural control technique. This method results in stable and robust running with the conceptual SLIP model which is extended by addition of a rigid trunk for upper body. Besides providing stability, this approach can represent the virtual pendulum (VP) concept which was observed in human/animal locomotion. Even more, the duality of this controller with virtual pendulum posture controller (VPPC) was mathematically shown. Such a mechanism could be also interpreted as a template for neuromuscular model.
bioRxiv (Cold Spring Harbor Laboratory), 2023
Human gait simulation plays a crucial role in providing insights into various aspects of locomotion, such as diagnosing injuries and impairments, assessing abnormal gait patterns, and developing assistive and rehabilitation technologies. To achieve more realistic results in gait simulation, it is necessary to utilize a comprehensive model that closely replicates the kinematics and kinetics of the human gait pattern. OpenSim software provides anthropomorphic and anatomically accurate human skeletal structures that enable users to create personalized models for individuals to accurately replicate real human behavior. However, torque-driven models face challenges in balancing unactuated degrees of freedom during forward dynamic simulations. Adopting a bio-inspired strategy that ensures an individual's balance with a minimized energy expenditure, this paper proposes a gait controller for a torque-deriven OpenSim model to achieve a stable walking. The proposed controller takes a model-based approach to calculate a "Balance Equivalent Control Torque" and uses the concept of the hip-ankle strategy to distribute this balance torque to the lower-limb joints. To optimize the controller gains and the "Balance Distribution Coefficients", an interface is stablished between MATLAB and OpenSim that is capable of conducting controllable forward dynamic simulations. The simulation results demonstrate that the torque-driven model can walk naturally with joint torques suitably matching experimental data. The robustness of the bio-inspired gait controller is also assessed by applying a range of external forces on the upper body to disturb the model. The robustness analysis demonstrates the quick and effective balance recovery mechanism of the proposed bioinspired controller. Forward dynamic simulation is a computational technique widely used in biomechanical systems to accurately simulate human movements[1-3]. This approach enables the model to closely replicate human behavior, including dynamic variables such as forces, torques, and motion trajectories[4]. To simulate human movements, various models have been used so far, ranging from simple mechanical models with biped models with low degrees of freedom to neuromuscular models, each with different capabilities[5-8].The OpenSim musculoskeletal human model is widely utilized for accurately simulating human movement and studying biomechanics[9]. It offers a detailed representation of the human body, including the skeletal structure and muscles[10]. Moreover, OpenSim skeletal models hold greater significance compared to mechanical models due to their anthropomorphic and anatomically accurate structure, as well as their scalability using motion capture[11]. However, the most critical challenge of torque-driven models are the existence of unactuated degrees of freedom and the requirement to implement an algorithm to maintain balance[12, 13]. In fact, in the forward dynamic simulation of the skeletal model of a human in
A controller for walking derived from how humans recover from perturbations
Journal of The Royal Society Interface
Humans can walk without falling despite some external perturbations, but the control mechanisms by which this stability is achieved have not been fully characterized. While numerous walking simulations and robots have been constructed, no full-state walking controller for even a simple model of walking has been derived from human walking data. Here, to construct such a feedback controller, we applied thousands of unforeseen perturbations to subjects walking on a treadmill and collected data describing their recovery to normal walking. Using these data, we derived a linear controller to make the classical inverted pendulum model of walking respond to perturbations like a human. The walking model consists of a point-mass with two massless legs and can be controlled only through the appropriate placement of the foot and the push-off impulse applied along the trailing leg. We derived how this foot placement and push-off impulse are modulated in response to upper-body perturbations in va...
Bioinspired template-based control of legged locomotion
2018
cient and robust locomotion is a crucial condition for the more extensive use of legged robots in real world applications. In that respect, robots can learn from animals, if the principles underlying locomotion in biological legged systems can be transferred to their artificial counterparts. However, legged locomotion in biological systems is a complex and not fully understood problem. A great progress to simplify understanding locomotion dynamics and control was made by introducing simple models, coined ``templates'', able to represent the overall dynamics of animal (including human) gaits. One of the most recognized models is the spring-loaded inverted pendulum (SLIP) which consists of a point mass atop a massless spring. This model provides a good description of human gaits, such as walking, hopping and running. Despite its high level of abstraction, it supported and inspired the development of successful legged robots and was used as explicit targets for control, over th...
Quasi-inverse pendulum model of 12 DoF bipedal walking
International Journal of Automation and Computing, 2017
This paper presents modeling of a 12-degree of freedom (DoF) bipedal robot, focusing on the lower limbs of the system, and trajectory design for walking on straight path. Gait trajectories are designed by modeling of center of mass (CoM) trajectory and swing foot ankle trajectory based on stance foot ankle. The dynamic equations of motion of the bipedal robot are derived by considering the system as a quasi inverted pendulum (QIP) model. The direction and acceleration of CoM movement of the QIP model is determined by the position of CoM relative to the centre of pressure (CoP). To determine heel-contact and toe-off, two custom designed switches are attached with heel and toe positions of each foot. Four force sensitive resistor (FSR) sensors are also placed at the plantar surface to measure pressure that is induced on each foot while walking which leads to the calculation of CoP trajectory. The paper also describes forward kinematic (FK) and inverse kinematic (IK) investigations of the biped model where Denavit-Hartenberg (D-H) representation and Geometric-Trigonometric (G-T) formulation approach are applied. Experiments are carried out to ensure the reliability of the proposed model where the links of the bipedal system follow the best possible trajectories while walking on straight path.
Heel-contact toe-off walking model based on the Linear Inverted Pendulum
5th IEEE RAS/EMBS International Conference on Biomedical Robotics and Biomechatronics, 2014
We propose a new heel-contact toe-off walking model based on the Linear Inverted Pendulum (LIP) model, which due to the linearity and the ease of manipulation of the equations, could be considered to be advantageous for a future online implementation for the generation of walking patterns. This new model is based on the so called functional rockers of the foot (heel, ankle and forefoot rockers), each of which are modeled as an inverted pendulum, changing the ground contact point position of the inverted pendulums for each rocker. We focus on the motion of the Center of Mass (CoM) in the sagittal plane, as it is the plane on which the rockers take place, but also generate the motions on the frontal plane. The model proved to work for constant velocity, accelerating and decelerating gaits, and the effects of the change of pivot point during heel-contact toe-off could be corroborated in the Zero Moment Point (ZMP) graphs. The implementation of this model could improve the human likeness of the motions, as well as the stability of the locomotion.
Control of Planar Spring–Mass Running Through Virtual Tuning of Radial Leg Damping
IEEE Transactions on Robotics, 2018
Existing research on dynamically capable legged robots, particularly those based on spring-mass models, generally considers improving in isolation either the stability and control accuracy on the rough terrain, or the energetic efficiency in steady state. In this paper, we propose a new method to address both, based on the hierarchical embedding of a simple spring-loaded inverted pendulum (SLIP) template model with a tunable radial damping coefficient into a realistic leg structure with series-elastic actuation. Our approach allows using the entire stance phase to inject/remove energy both for transient steps and in steady state, decreasing the maximum necessary actuator power while eliminating wasteful sources of the negative work. In doing so, we preserve the validity of the existing analytic approximations to the underlying SLIP model, propose improvements to increase the predictive accuracy, and construct accurate, model-based controllers that use the tunable damping coefficient of the template model. We provide extensive comparative simulations to establish the energy and power efficiency advantages of our approach, together with the accuracy of model-based gait control methods.
The Boundaries of Walking Stability: Viability and Controllability of Simple Models
IEEE Transactions on Robotics, 2018
From which states and with what controls can a biped avoid falling or reach a given target state? What is the most robust way to do these? So as to help with the design of walking robot controllers, and perhaps give insights into human walking, we address these questions using two simple 2-D models: the inverted pendulum (IP) and linear inverted pendulum (LIP). Each has one state variable at mid-stance, i.e., hip velocity, and two state-dependent controls at each step, i.e., push-off magnitude and step length (IP) and step time and length (LIP). Using practical targets and constraints, we compute all combinations of initial states and control actions for the next step, such that the robot can, with the best possible future controls, avoid falling for n steps or reach a target within n steps. All such combinations constitute regions in the combined space of states and controls. Farther from the boundaries of these regions, the robot tolerates larger errors and disturbances. Furthermore, for these models, and thus possibly real bipeds, usually if it is possible to avoid falling, it is possible to reach the target, and if it is possible to reach the target, it is possible to do so in two steps.
Foot trajectory approximation using the pendulum model of walking
Medical & Biological Engineering & Computing, 2014
Generating a natural foot trajectory is an important objective in robotic systems for rehabilitation of walking. Human walking has pendular properties, so the pendulum model of walking has been used in bipedal robots which produce rhythmic gait patterns. Whether natural foot trajectories can be produced by the pendulum model needs to be addressed as a first step towards applying the pendulum concept in gait orthosis design. This study investigated circle approximation of the foot trajectories, with focus on the geometry of the pendulum model of walking. Three able-bodied subjects walked overground at various speeds, and foot trajectories relative to the hip were analysed. Four circle approximation approaches were developed, and best-fit circle algorithms were derived to fit the trajectories of the ankle, heel and toe. The study confirmed that the ankle and heel trajectories during stance and the toe trajectory in both the stance and the swing phases during walking at various speeds could be well modelled by a rigid pendulum. All the pendulum models were centred around the hip with pendular lengths approximately equal to the segment distances from the hip. This observation provides a new approach for using the pendulum model of walking in gait orthosis design.